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bh=ottCArLuaQyqyYUtnXVtwFgrRFv9gwWZ98N0HEs0yrQ=; b=BSbKgWjqlTuU+K2jxi0BOekLiL/tslpF9Bjg1PDEpO00RwjuNHRhUQAQl2sb75pOD7 Le8OJGQ8g8b7GmTdDmPRGZLunzXtlpPWTCWLuRNQaOJXr2LZMRe+C/YL8Z9bR3S2I91j crlnTKcZ5zIRvd48DpUiM6djBJCzriwk4Mt1IwDsyMHCRFTx/VUu92GquDAZI4PJwAj9 FKzailTQQEMgha8fdPXnDAhmlKNG66ni4uc7wF/XfMXV8jpKtaD4gPu9tjSYbwvJR2qt 7C3xKLCM/Ao/CVD6OgB31dZLuRw0XkfpsHy4s2rBKDq18EKMi/R2YxdJ5etKKmkWXq3p oi2w== X-Gm-Message-State: AMCzsaV/2U6VVnZToCVi8mpFnJEskFsu4aa+CtkKcWOAf9Drpv5o2MyG mbPrghSPu3WZpuZtjT9b+jpElA== X-Google-Smtp-Source: ABhQp+Ticn2dcvOp9oZPmNwngdWCZ1U+syeWKSDoYNh8fNzCgrlX1O9hBfMa+QXeERX3vDt/Q7fpGQ== X-Received: by 10.107.11.27 with SMTP id v27mr9676557ioi.179.1509729162031; Fri, 03 Nov 2017 10:12:42 -0700 (PDT) Received: from samitolvanen.mtv.corp.google.com ([100.98.112.14]) by smtp.gmail.com with ESMTPSA id d186sm1370787itd.38.2017.11.03.10.12.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 03 Nov 2017 10:12:41 -0700 (PDT) From: Sami Tolvanen To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 04/15] kbuild: fix dynamic ftrace with clang LTO Date: Fri, 3 Nov 2017 10:11:48 -0700 Message-Id: <20171103171203.107569-5-samitolvanen@google.com> X-Mailer: git-send-email 2.15.0.403.gc27cc4dac6-goog In-Reply-To: <20171103171203.107569-1-samitolvanen@google.com> References: <20171103171203.107569-1-samitolvanen@google.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sami Tolvanen , Matthias Kaehlcke , Nick Desaulniers , Kees Cook , Greg Hackmann MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP With CONFIG_CLANG_LTO enabled, LLVM IR won't be compiled into object files until modpost_link. This change postpones calls to recordmcount until after this step. In order to exclude ftrace_process_locs from inspection, we add a new code section .text..ftrace, which we tell recordmcount to ignore, and a __norecordmcount attribute for moving functions to this section. Signed-off-by: Sami Tolvanen --- arch/Kconfig | 2 +- include/asm-generic/vmlinux.lds.h | 2 +- include/linux/compiler-clang.h | 7 +++++++ include/linux/compiler.h | 4 ++++ kernel/trace/ftrace.c | 6 +++--- scripts/Makefile.build | 14 +++++++++++++- scripts/Makefile.modpost | 4 ++++ scripts/link-vmlinux.sh | 16 ++++++++++++++++ scripts/recordmcount.c | 3 ++- 9 files changed, 51 insertions(+), 7 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 6b0c9d4de369..b82276a64045 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -617,7 +617,7 @@ config ARCH_SUPPORTS_CLANG_LTO config CLANG_LTO bool "Use clang Link Time Optimization (LTO)" depends on ARCH_SUPPORTS_CLANG_LTO - depends on !FTRACE_MCOUNT_RECORD + depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT select LD_DEAD_CODE_DATA_ELIMINATION help This option enables clang's Link Time Optimization (LTO), which allows diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index d0070985c191..99e794b8eec7 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -458,7 +458,7 @@ */ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ - *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + *(.text.hot TEXT_MAIN .text.fixup .text.unlikely .text..ftrace) \ *(.ref.text) \ MEM_KEEP(init.text) \ MEM_KEEP(exit.text) \ diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index 54dfef70a072..0f9fe03e5364 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -16,3 +16,10 @@ * with any version that can compile the kernel */ #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) + +#ifdef CONFIG_CLANG_LTO +#ifdef CONFIG_FTRACE_MCOUNT_RECORD +#define __norecordmcount \ + __attribute__((__section__(".text..ftrace"))) +#endif +#endif diff --git a/include/linux/compiler.h b/include/linux/compiler.h index fd8697aa4f73..94fe175a06e9 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -502,6 +502,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #define __visible #endif +#ifndef __norecordmcount +#define __norecordmcount +#endif + #ifndef __nostackprotector # define __nostackprotector #endif diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 8319e09e15b9..e117b849f9dc 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5573,9 +5573,9 @@ static int ftrace_cmp_ips(const void *a, const void *b) return 0; } -static int ftrace_process_locs(struct module *mod, - unsigned long *start, - unsigned long *end) +static int __norecordmcount ftrace_process_locs(struct module *mod, + unsigned long *start, + unsigned long *end) { struct ftrace_page *start_pg; struct ftrace_page *pg; diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 0cff240454f8..e69a02dec7bb 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -246,6 +246,12 @@ ifdef BUILD_C_RECORDMCOUNT ifeq ("$(origin RECORDMCOUNT_WARN)", "command line") RECORDMCOUNT_FLAGS = -w endif + +ifdef CONFIG_CLANG_LTO +# With LTO, we postpone running recordmcount until after the LTO link step, so +# let's export the parameters for the link script. +export RECORDMCOUNT_FLAGS +else # Due to recursion, we must skip empty.o. # The empty.o file is created in the make process in order to determine # the target endianness and word size. It is made before all other C @@ -254,17 +260,22 @@ sub_cmd_record_mcount = \ if [ $(@) != "scripts/mod/empty.o" ]; then \ $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)"; \ fi; +endif + recordmcount_source := $(srctree)/scripts/recordmcount.c \ $(srctree)/scripts/recordmcount.h -else +else # !BUILD_C_RECORDMCOUNT sub_cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \ "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \ "$(if $(CONFIG_64BIT),64,32)" \ "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CFLAGS)" \ "$(LD)" "$(NM)" "$(RM)" "$(MV)" \ "$(if $(part-of-module),1,0)" "$(@)"; + recordmcount_source := $(srctree)/scripts/recordmcount.pl endif # BUILD_C_RECORDMCOUNT + +ifndef CONFIG_CLANG_LTO cmd_record_mcount = \ if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" = \ "$(CC_FLAGS_FTRACE)" ]; then \ @@ -287,6 +298,7 @@ objtool_args += --no-unreachable else objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable) endif +endif # CONFIG_FTRACE_MCOUNT_RECORD # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index 2f3b45cbbe6b..da0c975ac4ed 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -164,6 +164,10 @@ lto_ko_objects = $(foreach o,$(1:$(modpost-ext).o=.o), \ $(shell [ -s $(@:.ko=.modversions) ] && \ echo -T $(@:.ko=.modversions)) \ -o $@ $(call lto_ko_objects, $(filter-out FORCE,$^)) + +ifdef CONFIG_FTRACE_MCOUNT_RECORD +cmd_ld_ko_o += ; $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) $@ +endif else cmd_ld_ko_o = \ $(LD) -r $(LDFLAGS) \ diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index c5c004b209ce..76e1da946f08 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -143,6 +143,19 @@ modpost_link() ${LD} ${LDFLAGS} -r -o ${1} $(modversions) ${objects} } +# If CONFIG_CLANG_LTO is selected, we postpone running recordmcount until +# we have compiled LLVM IR to an object file. +recordmcount() +{ + if [ -z "${CONFIG_CLANG_LTO}" ]; then + return + fi + + if [ -n "${CONFIG_FTRACE_MCOUNT_RECORD}" ]; then + scripts/recordmcount ${RECORDMCOUNT_FLAGS} $* + fi +} + # Link of vmlinux # ${1} - optional extra .o files # ${2} - output file @@ -327,6 +340,9 @@ if [ -n "${CONFIG_CLANG_LTO}" ]; then KBUILD_VMLINUX_INIT= KBUILD_VMLINUX_MAIN=vmlinux.o KBUILD_VMLINUX_LIBS= + + # Call recordmcount if needed + recordmcount vmlinux.o fi kallsymso="" diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 16e086dcc567..69a769904da7 100644 --- a/scripts/recordmcount.c +++ b/scripts/recordmcount.c @@ -420,7 +420,8 @@ is_mcounted_section_name(char const *const txtname) strcmp(".softirqentry.text", txtname) == 0 || strcmp(".kprobes.text", txtname) == 0 || strcmp(".cpuidle.text", txtname) == 0 || - strcmp(".text.unlikely", txtname) == 0; + (strncmp(".text.", txtname, 6) == 0 && + strcmp(".text..ftrace", txtname) != 0); } /* 32 bit and 64 bit are very similar */